Estimated capital costs to comply with existing and known federal and state air emissions regulations

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Number of Ameren Missouri Natural Gas Energy Centers Subject To IETL emission standards.

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Number of Days to Comply after Final EPA Determination

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The number of early energy center closures due to Illinois Energy Legislation

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Number of Energy Centers

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Number Of Energy Centers Closing Impoundments

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Number Of Energy Centers Closing Surface Impoundments

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Number Of Remediation Sites

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Number of Energy Center Scrubbers to achieve compliance with regulations

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Number of Energy Centers Constructing Wastewater Treatment Facilities

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Plant To Be Abandoned, Net

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Value established for a utility on which the entity is allowed to earn a particular rate of return

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Total costs accrued as of the balance sheet date for environmental loss contingencies.

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The carrying amount of a liability for an asset retirement obligation. An asset retirement obligation is a legal obligation associated with the disposal or retirement of a tangible long-lived asset that results from the acquisition, construction or development, or the normal operations of a long-lived asset, except for certain obligations of lessees.

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Commitments And Contingencies (Environmental Matters) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2021 USD ($) energyCenters scrubber site	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
Asset Retirement Obligation	$ 764	$ 756	$ 691
Coal Fired Electric Generation Equipment
Plant To Be Abandoned, Net	$ 604
Union Electric Company
Number of Energy Center Scrubbers \| scrubber	2
Number of Energy Centers Constructing Wastewater Treatment Facilities \| energyCenters	3
Number of Energy Centers \| energyCenters	4
Number of Energy Centers Closing Surface Impoundments \| energyCenters	2
Number of impoundments closing \| energyCenters	2
Number of Days to Comply after Final EPA Determination	135 days
Asset Retirement Obligation	$ 760	751	687
Number of Ameren Missouri Natural Gas Energy Centers Subject To IETL \| energyCenters	5
Number of Early Energy Center Closures \| energyCenters	1
Union Electric Company \| Coal Fired Electric Generation Equipment
Plant To Be Abandoned, Net	$ 604
Ameren Illinois Company
Asset Retirement Obligation	4	$ 5	$ 4
Ameren Illinois Company \| Coal Fired Electric Generation Equipment
Plant To Be Abandoned, Net	0
Manufactured Gas Plant
Accrual for environmental loss contingencies	$ 71
Manufactured Gas Plant \| Ameren Illinois Company
Number of remediation sites \| site	44
Accrual for environmental loss contingencies	$ 71
Minimum
Estimated capital costs to comply with existing and known federal and state air emissions regulations	125
Minimum \| Union Electric Company
Estimated capital costs to comply with existing and known federal and state air emissions regulations	125
Minimum \| Coal Combustion Residuals Estimate \| Union Electric Company
Estimated capital costs to comply with existing and known federal and state air emissions regulations	60
Minimum \| Manufactured Gas Plant \| Ameren Illinois Company
Estimate of possible loss	71
Maximum
Estimated capital costs to comply with existing and known federal and state air emissions regulations	175
Maximum \| Union Electric Company
Estimated capital costs to comply with existing and known federal and state air emissions regulations	175
Maximum \| Coal Combustion Residuals Estimate \| Union Electric Company
Estimated capital costs to comply with existing and known federal and state air emissions regulations	80
Maximum \| Manufactured Gas Plant \| Ameren Illinois Company
Estimate of possible loss	125
Rush Island Energy Center \| Union Electric Company
Rate Base	400
New CCR Rules Estimate
Asset Retirement Obligation	76
New CCR Rules Estimate \| Union Electric Company
Asset Retirement Obligation	$ 76